Bi-powered elevator brakes



Oct. 9, 1956 M. STALEY 2,765,874-

BI-POWERED ELEVATOR BRAKES Filed Oct. '7, 1953 3 Sheets-Sheet l F/nst Floor l0 Controls 24 INVENTOR. H

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BI-POWERED ELEVATOR BRAKES Filed Oct. 7, 1953 5 Sheets-Sheet 5 r1 3 {F3 W o2 r:r-\:r

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AT TOR NE YJ United States Patent 2,7ss s74.

BI-POWERED ELEVATOR BRAKES Marcellus Staley, Miami Beach, Fla., assignor to Staley Elevator Company, Inc, New York, N. 1., a corpcration of New York Application October 7, H53, Serial No. 334,688

14 Claims, (Cl. 187-29) This invention relates to elevators and more especially to apparatus for automatically stopping an electric elevator at the correct floor level regardless of differences in the duty of the elevator and variations in the friction of the brake. The invention is intended primarily for automatic elevators, such as are used in apartment houses and provided with push buttons by which the occupants of the house operate the elevator for themselves.

The object of the invention is to provide such elevators with higher possible speeds without giving up the efficiency of the single speed driving motor. This simplifies the equipment for comparable duties and reduces the first cost as well as maintenance.

It is an object of the invention to provide a simple and reliable apparatus for stopping an elevator operated by a single speed motor. The invention includes a load compensator such as disclosed in my Patent Number 2,173,289, issued September 19, 1939.

It is another object of the invention to provide a combination of brakes for stopping an elevator, with at least one of the brakes compensated for variations in load, and with a second brake for determining the exact location of the stop substantially independently of variations in the friction of the first brake.

One feature of the invention relates to the construction of the combined brakes, and to the electrically operated mechanism whereby the application of spring brakes is controlled, and a grip brake is applied to arrest the final motion of the elevator.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views;

Figure 1 is a diagrammatic side elevation of an elevator embodying this invention;

Figure 2 is a detailed view showing one modification of the invention;

Figure 3 is a top plan view taken on the line 22 of Figure 1;

Figures 4, 5 and 6 are graphs illustrating the operation of the invention;

Figure 7 is a greatly enlarged side elevation of the brake mechanism; and

Figure 8 is a wiring diagram for the invention.

The elevator 10 has a cross head 11 made of spaced channel irons. There are guide shoes 12 at opposite sides of the elevator which fit over the flanges of guide rails 15. Contact pins 16 are connected to the guide rails by brackets 17. These contact pins 16 are for the purpose of controlling the operation of the car when moving in an up direction. There are other contact pins 18 connected to the guide rail for controlling the operation of the elevator when moving in a down direction.

The guide rail on the other side of the shaft-way has contact pins 21 and 22 for controlling the final stopping of the elevator When moving up and down, respectively. These contact pins 21 and 22 are carried by brackets 24.

Fatented Oct. 9, 1956 All of the brackets 17 and 24 are adjustable for initially setting the controls to stop the elevator at the correct floor levels.

Figure 1 shows the elevator shaft extending for two floors, and the floor level controls are indicated by the legends, First floor; and Second floor. The car 113 is suspended by cables 27 connected to a cross tie 23 extending between the opposite side elements of a lever 30.

The lever 30 is pivotally connected to the cross head 11 by a shaft 31 extending through the lever and into brackets 32 on the cross head. The free end of the lever 3t} bears against springs 33 which resist upward movement of the free end of the lever 30. Thus, the full weight of the car is carried by the brackets 32 and the springs 33, and the compression of the springs 33 is proportioned to the load in the car.

A compensator lever 35 is attached to the cross head 11 by a fulcrum bracket 36. The right-hand end of this compensator lever 35 is attached to the lever 36 by a link 38, and the left-hand end of the lever 35 carries insulating blocks 41 and 42 (Figure 2) on which are mounted contact fingers 44 and 45 for wiping the contact pins 16 and 18 to establish control circuits as the car moves along the guide rails.

From the construction thus far described, it will be apparent that heavier loading or" the car compresses the springs 33 (Figure 1) and causes the compensator lever 35 to move counterclockwise around the fulcrum bracket 36. This causes the contact fingers 44 and 45 to be located closer to the car 10 when the car is heavily loaded, and further above the car when the car is lightly loaded. When the car is moving up, therefore, the contact fingers 45 will strike the contact pin 16, for a particular floor, later than when the car is lightly loaded. With a heavy load on the car, there is less upward slide after the brake is applied.

When the car is moving down, the movement of the contact fingers 45 closer to the car results in an application of the brake sooner, and this compensates for the additional momentum of the car which the brake must 1overlcome in order to stop the car at the intended floor eve On the opposite side of the car 10 there are insulating blocks 51 and 52 which carry contact fingers 54 and 55 for cooperation with the contact pins 21 and 22 to establish control circuits for a grip brake magnet which arrests the final motion of the car 10. These insulating blocks 51 and 52, and the contact fingers 54 and 55' which are carried by the insulating blocks, are on a short compensating lever 57 which rocks about a fulcrum bracket 58.

The short compensating lever 57 is connected to the lever 33 by a link 53 which causes the contact fingers and 55 to move downward, closer to the car it when the load on the car increases. The compensating movement of the contact fingers 54 and 55 with change in load on the car, is very much less than the compensating movement of the contact fingers 44 and 45, and in some embodiments of the invention, the insulating blocks 5i and 52 are mounted directly on the car with no cmnpensation for change in load.

he cables 27 extend upwardly in the elevator shait and pass over a cable drum 5? and then to a counter weight 60. The drum is driven by a motor 61 through reduction gearing 62. At one end of the motor shaft, there is a brake drum 54. A brake arm s5 is located in front of the brake drum 64, in Figure l, and this brake arm 65 rocks about a pivot stud 66 extending from a main frame 68 on which the drum 6% motor 61 and re duction gearing 62 are mounted.

There is a similar brake arm supported from a similar pivot behind the drum 64, and these brake arms are operated by magnetic coils 71 and 72 carried by an extension 73 of the frame 68. The brake will be described more fully in connection with Figure 7.

For the present it is sufficient to understand that the brake arms 65 are normally held together by spring pressure to apply the brake to the motor 61. When the etevator is to be operated, the spring brake is released in the conventional manner by energizing the spring brake coil 71. When the car is close to the correct floor level and moving at low velocity, the actual stopping of the car at the intended level is controlled by a grip brake actuated by the energizing of the grip brake coil 72. Actually, the spring brake and the grip brake operate the same brake shoes on the drum 64, but separate brake wheels and brake shoes may be used.

Figures 4, and 6 illustrate the principle of operation of the invention. In Figure 4, the curve represents the downward velocity of the car. At the point indicated by the legend spring brake, the magnetic coil, which holds the brake released, is tie-energized; and the car velocity decreases as indicated by the curve. If the spring brake alone were relied upon to stop the car, the velocity would decrease to zero along the dotted portion of the curve, and the car would stop a slight distance below the floor level. The contact pins along the shaft are adjusted so as to effect this result.

Just before the car reaches the floor level, at which the stop is to be made, the grip brake is applied at the point indicated by the legend grip brake, and the car velocity is arrested quickly in accordance with the solid curve from the grip brake point. The contact pins for the grip brake are adjusted so that the car stops exactly even with the floor level.

Figure 5 shows the operation of the elevator when there is a heavy load in the car. If the spring brake were applied at the point '75, which is the same level at which it is applied in Figure 4, and there were no grip brake for arresting the movement of the car, the velocity would decrease along the dot-and-dash line curve shown in Figure 5.

Because of the compensator lever, the spring brake is applied at a. point higher in the shaft, as indicated by the spring brake point on the solid line in Figure :3. Without the grip brake, the car would come to a stop in accordance with the solid and dotted curve; but with the grip brake applied at the point indicated, the final movement of the car follows the solid line and the car again stops exactly even with the floor level. The point of application of the grip brake, in Figure 5, is substantially the same as in Figure 4-. Any increase in car load is proportionally adjusted to thus apply the brakes.

Variations in the level at which an elevator car stops depend also upon factors other than the load on the car. The temperature of the atmosphere, and moisture, affect the friction of the elevator brake shoes. When the elevator has been used more or less continuously for a period of time there is a heating of the brake shoes and drum which affects the friction.

Figure 6 shows the operation of this invention under conditions of wide variation in the brake friction. The conditions assumed for Figure 6 are the same as those for Figure 5 except that there has been a substantial decrease in the friction of the brake. Without the grip brake, the elevator car would slow down in accordance with the solid curve between the spring and grip brake points, and would finally stop in accordance with the dotted line curve. The stop level would be substantially lower than in Figure 5 because of the reduced brake friction.

With the grip brake of this invention, applied at the same point as in Figure 5, the stopping of the elevator in Figure 6 follows the solid line curve from the grip brake point and stops substantially level with the floor. Because of the fact that the car velocity is somew tat higher when the grip brake is applied, in Figure 6 as compared to Figure 5, and the additional fact that the friction of the grip brake is less when the coefiicient friction of the spring brake is reduced, the difference in the level of the car stop is very small. The rapid deceleration effected by the grip brake is not objectionable to the passengers because the car is moving with very low velocity when the grip brake is applied; and as a result of the small vertical component of the grip brake curve, friction variations effect the stopping of the car by the grip brake much less than in the case of the spring brake.

For example, a difference of 10 percent in the slide of the car, when relying upon the spring brake alone, will cause the car to stop at .a level which varies substantially from the floor level. However, a similar percentage of variation the slide, while the grip brake is applied, produces a hardly noticeable variation in the final level of the stop. Thus, the combination of the relatively slow action of the spring brake with the rapid final stopping by the grip brake produces a simple and reliable means for obtaining accurate correspondence of thc car level with the floor level. In Figures 4-, 5 and 6, the velocity of the car, at the time the grip brake is applied, is exaggerated for clearer illustration.

The practical application of this invention results partly from the fact that the kinetic energy to be absorbed by the brakes varies as the square of the velocity of the car. When the velocity of the car is cut in half, the remaining kinetic energy to be absorbed is only onequarter of the original kinetic energy. Likewise, a reduction in the car velocity, from 150 feet per minute to 15 feet per minute, leaves only one one-hundreth of the original kinetic energy still to be absorbed in bringing the car to a stop. The use of the mechanical levers in the load compensator are shown for descriptive purposes only. Other methods such as hydraulic may be used as shown in Patent No. 2,173,289.

Figure 7 shows one construction of the brake. There is a brake shoe 81 attached to each of the brake arms 65 by a pin 82. The brake shoes 31 have brake linings 83, in accordance with conventional practice. A rod 85 extends through slots 36 in the brake arms 65. A head 87, at one end of the rod 35, and nuts 82 at the other end of the rod 85, compress springs 9% against the brake arms 65 to force the brake shoes Ell against the brake drum 64.

At the upper ends of the brake arms (i5 there are links 92. The inner ends of these links 92 connect with a frame 93 attached to the lower end of a rod This rod 95 is preferably threaded at its lower end and provided with nuts for holding the frame 9-3 at any adjusted position along the line of the threads on the rod 95.

There are magnet plungers 97 and 98 carried by the rod 95 at pro-determined levels above the frame 93. The plunger 97 is located at the lower portion of the magnetic coil 71, and the plunger 58 is located at the upper portion of the coil '72.

Because of these locations of the plungers 97 and 98, with respect to the magnetic coils '71 and '72, respectively, the plunger 97 is drawn upwardly when the coil "7i is energized, and the plunger 93 is drawn downwardly when electrical energy is supplied to the coil 12. The plungers 97 and 98 are preferably rigidly connected to the rod 95 so that the rod 95 moves as a unit with the plungers.

The rod 95 slides in frame members which keep the rod in line with the coils 71 and 72. When the rod 95 is at the lower end of its stroke, the frame 93 is located so that the links 92 slope downwardly toward the frame 93. When the coil '71 is energized, the plunger 97 and rod 95 are drawn upwardly. This moves the links M to decrease their angle with the rame 93 and thus presses the upper ends of the brake arms 65 away from one another. This movement, against the compression of the springs 90, opposes the pressure of the brake shoes 81 on the drum 64 and thus releases the brake. Whenever the supply of current to the coil 71 is shut off, the magnetic field of the coil 71 decays rapidly and the springs 9% apply the brake.

When the coil 72 is energized, it moves the plunger 98 and rod 95 downwardly, and this downward movement pushes frame 93 carrying the inner ends of the links 92 downward and urges the upper ends of the brake arms 65 toward one another. This adds to the pressure of the springs 90 and thus increases the friction of the brake shoes 81 against the drum 64. Thus, de-energizing of the coil 71 applies the spring brake to the drum 64, and energizing of the coil 72 applies the "grip brake to the drum. Any other conventional release brake system can be utilized.

Figure 8 shows the wiring diagram for the invention. In this figure, the contacts operated by the various relays are shown separated from one another so as to simplify the wiring diagram, and the identification of the contacts with the operating coils of their relays is indicated by the use of common letter reference characters for the various parts of each relay.

The wiring diagram is for a simple automatic push button elevator system for three floors; but it will be understood that the system can be used for any number or" floors merely by duplicating the various controls for the additional floors.

Push buttons P1, P2 and P3 are provided for the respective floors. A non-interfering relay 1 is provided to cut out all push buttons after one push button has been pressed and the elevator car has moved in response to the operation of that push button.

A commutator mechanism CO is shown in the drawing, and it is one of the ratchet type commonly used for automatic elevators. The usual ratchet gear for the commutator drive has a set of teeth corresponding to the number of floors that can be reached in the up direction, and a set of teeth corresponding to the number of floors which can be reached in the down direction of travel.

Up and down jump relays ED and EU are provided to actuate ratchet pawls for engagement with the ratchet gear to rotate the commutator in the direction corresponding with that of the moving car. The pawls and ratchets are not shown in the wiring diagram since they are conventional structure, well known in the art, and their illustration is not necessary for a complete understanding of this invention. The jump magnet EU is energized by the rail contacts 16 which cooperate with the contact finger 44 on the car when the car is traveling upwardly. This establishes a momentary circuit for the jump magnet EU and the stopping distance in advance of each floor the car is approaching. Contacts 18 along the rail co-operate with the contact finger 45 on the car to momentarily energize the jump magnet ED when the car is traveling in the downward direction.

The commutator mechanism CO comprises a plurality of sections. A floor section F is employed to control the floor relays F1, F2, and F3; and it consists of two metal portions and a neutral section. The metal portions establish the circuits for all of the floor relays by contact with brushes 1F, 2F and 3F, except for the floor relay at the landing where the elevator car is currently positioned. Brushes FU and FD connect the metal sections to the negative side of the power line.

The commutator mechanism also includes dispatch section D1 which is similar to the floor relay section F; and this dispatch section has brushes 81D, 2D and 3D which are in circuits with contacts 2P1, 2 F2 and 2E3, respectively, controlled by the respective floor relays. The dispatch section has other brushes DU and DD which are in circuits .with the up and down relays U and D. The metal portions of the floor section and the dispatch section of the commutator mechanism are so positioned with respect to the brushes that the particular brushes for the floor, Where the elevator car is currently located, are

6 not in contact relationship with the metal portions of the commutator mechanism.

The wiring diagram shows the contact pins 21 and 22 located at different levels along the elevator shaft. These contacts are designated by legends indicating the particular floor stop for which they are effective. Thus, 21 (2nd) indicates that the particular contact pin 21 is for controlling the operation of the elevator car at the second floor. Contact fingers '54 and 55, on the elevator car, momentarily close circuits with the contact pins 21 and 22 as the elevator car passes these pins along the shaft.

The operation of the system may be illustrated by as suming that a person enters the elevator car on the 3rd floor, closes the landing door and gate, and presses the button 2P for making the elevator travel downwardly to the 2nd floor. A circuit is then completed from the line L1, at the left of Figure 2, through the non-interfering relay contact .11 push button P2 and floor relay coil F2 to the contact brush 2F of the commutator mechanism. The circuit continues through one section of the drum F to the brush FD and to the other side of the line L2. The establishing of this circuit energizes the floor relay F2.

When this door relay F2 is energized, it .closes its associated contacts 1F2 and 2P2. The contact 1F2 controls a holding circuit for the relay F2 so as to keep the circuit closed after pressure on the push button P2 is released. The contacts 2P2 complete a circuit for the down direction magnet D. This latter circuit extends from the negative side of the line L1 through the door switch, gate switch, emergency switch E81, and through contacts 2P2 to the associated brush 2D of the dispatch section of the commutator mechanism. The circuit then continues through this section of the commutator mechanism to the brush DD and through cont-acts U1 and down direction magnet D to the other side of the line L2. It will be understood that if any other push button is pressed, a floor relay corresponding to the pressed button is energized to close its associated contacts, corresponding parts for the different floor controls having similar reference characters with numerals designating the particular floor.

The down direction magnet D, when energized, opens contacts D1, and closes contacts D2, D3, D4, D5 and D6. The norma-lly clo-sed cont-acts D1 provide a safety interlock for the up magnet U. Contacts D2, when closed, complete the circuit for the non-interfering relay I which is energized to open the contacts 11 and disconnect all of the push buttons from the line L1.

The contacts D3, when closed, prepare a circuit for the down jump magnet ED, and the contacts D4 and D5 complete the circuit to the release-brake magnet coil 71 and motor 61. The circuit for the release-brake magnet 71 and the motor 61 can be traced from the line L2, through contacts D4, brake release magnet 71, and contacts D5 back to line L3. The contacts D4 and D5 also connect the line L2 and line L3 to the motor 61.

When the brake magnet 71 is energized, it attracts the plunger '97 (Figure 7) and operates the arms 64 to release the brake, as previously explained. With the brake released and with power supplied to the motor 61, the elevator car moves downwardly toward the 2nd floor. During this downward travel, the finger 45 on the car mak s a momentary contact with the pin '18 (2nd) in the elevator shaft and establishes a momentary circuit to energize the down jump magnet ED. This circuit is traced from the line L1 to guard rail 15, contact pin 18 (2nd), finger '45, contacts D3, and down jump magnet ED move-s the commutator mechanism into position corresponding to the location of the elevator car at the second floor.

The commutator brushes 2F and 2D are then positioned over the neutral areas between the metal port-ions of the floor and dispatch sections of the commutator mechanism, thereby opening the circuit to the relay F2 and to the magnet D. The contact-s D4 and D5 are 7 opened to shut off power to the motor 61 and to the release brake magnet 71. The springs of the brake apply the brake to the elevator motor. With the brake applied, the car slides for a distance along the guide rail with gradual deceleration so that no discomfort to the passengers will occur.

When the down magnet D becomes de-energized, the contacts D6 were closed to prepare a circuit for the brake relay BZR; and this circuit is completed when the contact finger 55 on the elevator car touches the pin 22 (2nd), located along the other guard rail of the elevator shaft. This contact of the finger 55 with the pin 22 (2nd) momentarily energizes the brake relay B2R1 to establish a holding circuit for the relay, and contacts B'2R2 are also closed 'by the relay 132R to complete -a circuit for the grip brake magnet coil 72.

The circuit of the brake relay BZR can be traced from the line L1, through the door switch, guide rail 15, contact pin 22 (2nd), contact finger 5'5, and closed contacts D6 and U6, and through the coil brake relay B2R to line L2. The holding circuit for the brake relay is traced from the line L1 through the door switch, through contacts B2R1 and to the coil of the relay BZR.

When the grip brake magnet 72 is energized, it operates the brake arms to apply substantially increased pressure of the brake shoes against the drum to make the brake quickly absorb the reduced momentum of the elevator car so that the car is brought to a stop at a level which corresponds accurately to the level of the floor, as previously explained.

When the passenger leaves the elevator car, he opens the gate and the landing door. This opens the gate switch and the door switch. The opening of either of these switches or any other conventional means de-energizes the grip brake BRZ to open circuit brake magnet 72 and leaves the brake applied only by the springs of the brake mechanism.

The preferred embodiment of the invention has been illustrated and described with a simple wiring diagram to illustrate the principle of operation, but various changes and modifications can be made without departing from the invention as described in the claims.

What is claimed is:

1. An automatic elevator system comprising an elevator car for travel up and down in a shaft, operating mechanism for raising and lowering the car in the shaft, brake means for stopping said mechanism including an actuator that biases the brake means to apply the brake, a first power device operable to oppose the bias of said actuator and to release the brake means, a second power device operable to assist the bias of the actuator to increase the gripping pressure of the brake means, control means carried by the car for cooperation with floor indicating devices located along the shaft, the control means including controllers connected with the first power means and responsive to the first power means to the bias of the brake actuator, a support connecting said control means with the car, said support being movable with respect to the car in the direction in which the car travels and in proportion to the load in the car, and the control means including controllers connected with the second power means and responsive to the indicating devices to increase the gripping pressure of the brake, the controllers for the brake bias application being in position to respond to the indicating devices ahead of the controllers for the brake gripping pressure.

2. The automatic elevator system described in claim 1 and in which said other controllers for the increased brake gripping pressure are also connected with the car by a support that moves said other controllers toward and from the car in the direction in which the car moves and in proportion to the load on the car, the movement of the controllers connected to the first power means, for any change in load, being substantially greater than the corresponding movement of said other controllers.

3. An automatic elevator system comprising an elevator car for travel up and down in a shaft, operating mechanism for raising and lowering the car in the shaft, 21 friction brake for stopping the operating mechanism with the car at different floors, a spring for applying pressure to the brake, a first power device that releases the spring pressure when energized, a second power device that adds to the spring pressure when energized to supply an extra gripping pressure to the brake, controllers carried by the car and in the circuit of the first power device, other controllers and in the circuit of the second power device, and floor indicators at predetermined locations along the shaft in position to operate said controllers and said other controllers respectively, in a predetermined sequence.

4. The automatic elevator system described in claim 3, characterized by supports connecting the controllers and said other controllers to the car, the supports being movable to shift said controllers and said other controllers toward and from the car in the direction of movement of the car, the supports being connected to cables that lift the car and having spring means opposing downward movement of the elevator so that the movement of the supports toward and from the car depends upon the load in the car and resulting compression of the spring means.

5. The combination with an elevator car having cables by which the car is raised or lowered in a shaft, a lever to which the cables are connected, a pivotal connection between the lever and the car, a spring reacting upward against the car and resisting the rocking movement of the lever about the pivot, by the pull of the cables, so that movement of the lever about the pivot is proportional to the load in the elevator, two separate brake actuators, different controllers for the separate brake actuators, floor indicators that operate the separate brake actuators successively, the controller for the first operated brake actuator being carried by the lever for movement with respect to the car with an up and down component in response to changes in the load in the car.

6. An elevator system including a car, mechanism for raising and lowering the car including motor-operated mechanism, brake means for stopping said mechanism when the car reaches various floor levels, the brake means including a drum, friction means that bear against the drum, arms connected with the friction means and movable with respect to one another to apply and release the brake, spring means urging the arms in direction to apply the brake, a first magnet that urges the arms to move in directions to release the brake, and a second magnet that urges the arms to move in directions to apply the brake, and means located at spaced stations along the path of movement of the car for controlling the energizing of the magnets when the car reaches predetermined locations with respect to the floor levels.

7. The elevator system described in claim 6 with different circuit controllers on the car responsive to the passing of the means at the spaced stations, the different controllers being movable with respect to the car with an up and down component of movement and in response to changes in the load in the car, yielding means resisting movement of the different controllers in response to the load in the car so that the movement is proportioned to the load.

8. An elevator system including a car, mechanism for raising and lowering the car including motor-operated mechanism, brake means for stopping said mechanism when the car reaches various floor levels, the brake means including a drum, friction means that bear against the drum, arms connected with the friction means and movable with respect to one another to apply and release the brake, spring means urging the arms in directions to apply the brake, a vertically movable frame between the arms, links connecting the frame with both arms, the links extending at acute angles to the direction of movement of the frame so that movement of the frame changes the angularity of the links and moves the arms closer together or apart depending upon the direction of movement of the frame, magnetic means that move the frame in a direction to release the brake when the magnetic means are energized, and other magnetic means that move the frame in the opposite direction when energized to add to the force of the spring in applying pressure to the brake.

9. The elevator system described in claim 8 characterized by brake arms that swing about pivot axes extending substantially horizontally and parallel to the axis of rotation of the drum, and that swing toward one another to apply the brake, a rod extending through the arms above the drum with springs compressed between the outside surfaces of the arms and abutments on the ends of the rod, a vertically movable frame between the arms above the rod, separate links connecting the frame with the respective arms, the links extending at acute angles to the direction of movement of the frame so that movement of the frame changes the angularity of the links and moves the arms closer together or apart depending upon the direction of movement of the frame, a substantially vertical rod to which the frame is secured, guides in which the rod moves up and down, two solenoids disposed one above the other in axial alignment with the rod and with each other, plungers carried by the rod and in the solenoids, the plunger of one solenoid being in its centered position in the solenoid when the frame is in a position to release the brake, and the plunger of the other solenoid being in its centered position in the solenoid When the frame is in a position to increase the pressure of the springs to supply added gripping friction to the brake.

10. The combination of an elevator car having cables by which the car is raised or lowered in a shaft, a supporting member that yields with amplified re-actionin proportion to the load on the car, the supporting member being attached to the car and carrying brake actuating contacts, a brake for said elevator, braking means for applying pressure upon said brake for absorbing the momentum of the elevator car gradually, and additional braking means for arresting the remaining momentum of the elevator car at predetermined locations in the shaft, different controllers for the separate brake actuators, and

10 floor indicators that operate the separate braking means successively.

11. An electric elevator system comprising an elevator car that moves up and down in a shaftway, means supporting the elevator car including a mechanism that weighs the load on the car, an electromagnetic brake, control means for applying mechanical friction to the brake at a distance ahead of the proposed stop, the distance being proportional to the load measured by weighing means, and other brake means to increase the friction of the brake to cause a soft stopping of the car at precise points in the shaftway.

12. An elevator system comprising an electric push button operating control, the car of which is equipped with a yielding member movable in proportion to the load, and carrying switches to cooperate with fixed members attached to the hatchway, an electrically released and an electrically pressurized brake on the driving motor operable by those switches in sequence to stop the car at predetermined positions in the hatchway.

13. On an electric elevator consisting of a car, and the operating mechanism including a friction brake, a

ielding member on the car operable in proportion to the load, said yielding member carrying units to operate in connection with fixed members located in the hatchway, to actuate the stopping of the car by first applying a fixed amount of retarding friction to the brake and then after a sufficient interval, make a second additional application of friction to produce an accurate stop.

14. On an electric elevator having an automatic control system with means to apply the stopping brake during an interval proportioned to the load on the car to gradually absorb the momentum of the car, an additional means to increase the friction upon the brake to arrest the sliding car at exact positions along its travel.

References Cited in the file of this patent UNITED STATES PATENTS 2,173,289 Staley Sept. 19, 1939 2,403,125 Santini July 2, 1946 2,664,546 Doolan July 7, 1953 

